U.S. Pat. No. 3,065,949 dated Nov. 27, 1962 to Joseph H. DeFrees and entitled Chemical Emergency Valve, discloses a type of emergency valve which attempts to provide greater simplification in the cleaning operation of the valve, with the latter being accomplished by presenting a valve structure wherein the working parts are enclosed, so as to be out of contact with the liquid being carried, charged or discharged from the tank.
Various other emergency type valves are known in the art, such as for instance U.S. Pat. No. 3,910,551 in the name of Joseph H. DeFrees issued Aug. 23, 1977; Canadian patent No. 654,932 in the name of Joseph H. DeFrees and issued Jan. 1, 1963 and entitled Bottom Loading Emergency Valve; and Canadian patent No. 654,916 dated Jan. 1, 1963 and entitled Chemical Emergency Valve. However, in all of these prior art valve assemblies, the disassembly, inspection and cleaning thereof represents quite a time consuming task and thus an undesirable situation in the operation of inspecting and cleaning the valves between loads so as to attempt to prevent contamination between such loads.